IPTV Trick Streams : The Slight-Of-Hand of Modern Video On Demand Delivery
IPTV services have taken a major bite out of the market share of traditional cable, with brands like UVerse / FiOS in the US, and Optik TV / Fibe in Canada. IPTV is short for Internet Protocol Television, which is essentially TV service delivered over an internet connection versus the traditional ‘cable’ methods of delivery.
TV service generally falls into two major categories, linear content which most will recognize as traditional television channels, and video on demand or VOD, which emulates the experience of watching a DVD or Blu-Ray on your television. These service delivery concepts are generally easily understandable, however some implementation details can be quite surprising, in particular how VOD content emulates seeking to different parts of the particular video title.
When you order a VOD title from your TV service, at a high level the process is similar to watching a video file on your computer. The major difference is that the video file is stored with your TV provider, and your set-top box functions as a computer, delivering the video content to your television. Slightly different than watching a movie on your computer, but no surprises yet.
The surprise comes in the form of trick streams. Trick streams are video files that contain the complete VOD title, but are played back at different speeds. These speeds are generally between 2x - 16x the normal speed, which enables you to see the part of the movie you are navigating to versus just seeing the time index. If it was not necessary to mimic the VCR user experience in being able to see the movie as you scan through different times, trick streams would likely not be necessary.
In examining how trick streams are created, we have to examine how video titles are ingested. Ingestion is a process involving a video file being input into the TV service middleware. Middleware functions as a software layer between the customer’s set top box and the video content itself. There are many different middleware products for television delivery currently available.
When a raw video file is ingested, it is made ready for delivery to set-top boxes. The video or audio formats may be changed for better content delivery, and trick streams will be created. These often exist as separate video files with the audio stripped out since it will not be played back to the consumer during seeking to different time indexes in the video content.
When you press the fast-forward or rewind button, the video stream switches to the trick stream matching the seeking speed (ie 2x, 4x, 8x, etc). As you increase the speed, the video display will again switch to the matching trick stream. This continues until you eventually hit the play button, at which time the set-top box will return to the original video title, including audio. This technology has also be applied to linear content such as rewinding live TV, although in this case the stream conversions happen locally on the set-top box.
Current IPTV offerings are often heavily steeped in flashy user interfaces, innovative features and integration with the latest consumer devices such as tablets and phones. In contrast, trick streams are a bit of backstage deception, using the process of skipping between different digital files to deliver a user experience that the public has come to expect from their familiarity with the analog technology of the past. When you order your next movie or on-demand television show, say a little thank you to the 4 or 5 digital files working hard in the background to let you skip to the good parts.